1 J2 HYMENOPTERA OF AMERICA. [PART I. 



-lender appearance. The first segment of the abdomen 

 is often quite strongly punctured and even sometimes divided by 

 a groove. We possess many males of very small size (length 



" mm.) and quite slender, taken by Edward Norton in the 

 environs of New York and in Massachusetts, which offer very 

 slender yellow markings, and in winch the metathoracic ridges 

 are quite blunted. One, however, recognizes them by their 

 enlarged antennae, yellow beneath at the extremity. With this 

 species the borderiug of the prothorax is narrow, a little bilobed, 

 terminating to a point on each side. Sometimes the metathorax 

 is but little angulate, while the superior ridges are also more 

 arcuate. 



Bess. a. diff. — This species is recognized by its form, very 

 slender and elongate, but yet different from that of 0. fuh 

 in that the thorax is flattened above and the abdomen beneath, 

 as with the 0. capra and its congeners, not cylindrical as with 

 the 0. fulvipes and its neighbors. In its livery it resembles the 

 mpestris, but is distinguished from it by its very much more 

 slender form, by the very sharp ridges bordering the metathorax, 

 by the first segment having the border not enlarged upon the 

 sides, e.te. The very small males could be easily confounded with 

 those of the O. Philadelphise, but can be easily distinguished 

 from them by the wide and short form of the superior face of the 

 l\v<{ segment and by the absence of its great longitudinal groove. 



Hab. Tbe United States. Canada. (Lake Superior.) Con- 

 necticut. New York. Pennsylvania. Illinois. Louisiana. The 

 Prairies. (Fort Tejon.) (14 ?, 10 I.) 



9. A. ambiguus Spin. — Niger, punctatus ; metanoto rngoso, exe.ivato, 

 acute marginato, utrinqne angulato : antennis snbtus rufis ; pronoti mar- 

 gine antico, macula subalari, et scntelli, abdominis segmentorum 1\ 2* 

 margine postico, luteis ; secundo subtus basi tuberculato ; alia rnfes- 

 centibns, apice griseis, tegulis flavo-margiuatis ; £ clypeo llavo, tibiis 

 et tarsia rnfis ; scntello et pleuris nonnumiuam immaculatis. 



" - - in., Gay's Bist. fis. de Chile, Zool., Vr, 264, 9 (1851) 



9-— > • ' ss. Vesj : les, I. He. 23, 9. 



1. Bustillos - . Say's, Chili, it. id. 507,10. t, .— Sacss. Yespules, 



1. 141, 25, ' : HI. - 



9. Total length, 9.5 mm. ; wing, 6.5 mm. 

 £ . Total length, 7 mm. ; wing, 5.5 mm. 





